Perry, John (1850–1920), engineer, physicist, and educational reformer, was born 14 February 1850 in Garvagh, Co. Londonderry, second son of Samuel Perry of Garvagh and his wife Agnes (née Smith; d. 1905). His father was a house painter and glazier in Garvagh, before taking his family to Belfast in search of work, and published a book of historical poetry in the year that John was born. There were also three daughters. John's elder brother James Perry (1845–1906) became county surveyor for Galway, set up an electricity supply company for the city of Galway, worked to preserve ancient monuments, and was a pioneer photographer; he was father of Alice Perry (qv).
John was educated for a short time in Garvagh, then at the Model School, Belfast, and from 1864 to 1868 served an apprenticeship at the Lagan Foundry, Belfast. From 1868 to 1870 he attended the engineering classes given by James Thomson (qv) at QCB, while working in the foundry during the summer months. Overwork led to eyestrain and threatened blindness, but thanks to his sister's help in reading textbooks to him he was able to graduate B.Eng. (1870), obtaining a first-class degree and gold medal. In the same year he won a Whitworth scholarship and accepted a post as mathematical master and lecturer in physics at Clifton College, Bristol, where he established what was probably the first school physics laboratory and workshop. In 1874 he was appointed assistant to William Thomson (qv) at Glasgow University, leaving in the following year to take up a professorship at the Imperial College of Engineering, Tokyo, Japan; it was held jointly with William Ayrton. Their lectures provided an important stimulus to Japan's industrialisation. The two men built up a productive partnership and between 1876 and 1879 jointly published almost thirty papers on topics such as electricity, heat conduction, stresses, and earthquakes.
On his return to England (1879) Perry became examiner in engineering to the City & Guilds of London Institute, and in 1882 was appointed professor of mechanical engineering and applied mathematics at the City & Guilds of London Technical College in Finsbury. Along with his colleagues at Finsbury (William Ayrton and H. E. Armstrong), Perry helped revolutionise technical education in England, emphasising practical instruction, and hoping that it would be possible to bridge the gap between engineers and mathematicians. He wanted engineers to think scientifically, and mathematicians to be able to visualise their formulae in terms of concrete facts. Perry and Ayrton popularised squared paper as a teaching aid and as an important adjunct in measurement and data recording; they had first found it of assistance in their Japanese classes, and subsequently had it printed in large quantities to reduce its price. The introduction of squared paper to classrooms was an important aspect of the ‘Finsbury method’ in the 1880s, and is perhaps Perry's most lasting legacy to science education; it helped encourage the wider use of graphs as diagrams in scientific papers.
Perry was appointed professor of mathematics and mechanics at the Royal College of Science, London (1896). His textbooks The calculus for engineers (1897), Applied mechanics (1897), and Steam and practical mathematics (1899) were noted for their practical approach and their lack of dependence on abstract reasoning, and they enjoyed lasting popularity. In 1899 the board of education, on his suggestion, established ‘practical mathematics’ as an examination subject. His polemical England's neglect of science (1901) castigated the non-progressive nature of technical instruction in England, urging that it was necessary to make elementary mathematics teaching more practical and correlated with an experience of laboratory-based science. He was particularly opposed to the emphasis on Euclidean geometry in the teaching of mathematics, which he believed was merely a pedantic remnant of the influence of classical studies on education generally.
In 1881 Perry was awarded the silver medal of the Royal Society of Arts for his lecture ‘The future development of electrical appliances’. Among his many patents and inventions, his contributions to electricity, especially electrometry, were most notable. Ammeters, voltmeters, and an important spring device used for calibrations were developed in cooperation with Ayrton; Perry's commercially successful electricity supply meter for domestic use was developed after their partnership was dissolved in 1889. He collaborated with his brother in developing hydroelectric power generation in Galway. In 1885 he became engineer to the Telpherage company and superintended the construction of the Telpher line at Glynde, Sussex; it carried clay for about a mile in wagons suspended from a cable, and was the first electrically powered aerial railway in the world.
Perry became a fellow of the Royal Society in 1885, and was awarded the degree of D.Sc. by the RUI. In 1914 he represented the British government on the South African university commission. He was treasurer of the British Association from 1904 until his death, and was also president of the Institute of Electrical Engineers (1900–01) and of the Physical Society (1910–11). Perry was well known in scientific circles, and was friendly with George F. Fitzgerald (qv), Joseph Larmor (qv), and other leading physicists.
Perry privately published (1894) On the age of the earth, a response to an influential work by his former boss, William Thomson, who had worked out an age for the earth, based on known rates of cooling. Perry suggested that convection in the earth's interior would invalidate these calculations. If more scientists of the day had been aware of Perry's book, published at least fifty years before the development of a theory of continental drift, his conclusions might have enabled geologists to challenge the theoretical framework underpinned by Thomson's assumptions and have constituted an important contribution to geodynamics. He died 4 August 1920 in London.
He married (1879) Alice Jowitt (d. 1904) of Sheffield; they had no children. He was buried beside her in the churchyard at Wendover, Buckinghamshire, where they had a country cottage.